The power distribution industry uses a network of transmission lines to distribute electrical power to homes, businesses and industry. It is important that the electrical power be supplied continuously and at a stable voltage level. If the supply of power flickers and is not continuous, then consumers will see their lights flicker and other electrical equipment such as computers may malfunction. The voltage level must likewise be stable for the proper operation of electrical equipment.
A problem that utilities encounter comes from the changing electrical loads of their consumers. When large electrical equipment in a factory is turned on, for example, the increased electrical load will have the tendency to reduce the voltage level of the supplied power. Likewise, when the equipment is turned off, the decreased electrical load will tend to increase the voltage level of the supplied power. The same is true with large home appliances such as air conditioners, particularly when the air conditioners in adjacent homes are turned on in close proximity.
To compensate for the changing voltage levels caused by changes in electrical load, power companies install voltage regulators to raise the voltage level in response to an increase in load and to decrease the voltage level in response to a decrease in load. This is commonly accomplished within the voltage regulator by providing a number of taps on a circular path. A neutral tap leaves the voltage unchanged. A number of raise taps separately raise the voltage in fixed steps corresponding to each raise tap. A number of lower taps lower the voltage in fixed steps corresponding to each lower tap. An arctuate electrical contact is designed for contacting a particular tap to set the output voltage of the regulator. A motor drives the taps along the circular path in order to position the appropriate tap in electrical connection with the arcuate contact. During the transition from one tap to the next, the arctuate contact overlaps adjacent taps so that there is no discontinuity or flicker in the output voltage. A control circuit senses the output voltage with a potential transformer and then controls the motor to select the appropriate tap.
In use, voltage regulators must be tested to ensure that the effects of age, wear and corrosion do not cause flickers in the output voltage during tap changes and to ensure that the output voltage is being properly sensed by the potential transformer.
The present invention relates to a test set for testing the voltage regulators commonly used by utilities in power distribution systems. In particular, the test set tests the operation of a voltage regulator in raising and lower its load voltage and in sensing the load voltage with a potential transformer. Other tests can also be performed.
Conventional apparatus for testing a voltage regulator in the power industry includes a discrete voltmeter, source of electrical power, lamp and socket with jumpers for testing continuity, and multiple jumpers. During a test of the potential transformer within a voltage regulator, the power source is connected with jumpers across the load and S/L bushings. The voltmeter is also connected with jumpers across these bushings. The power source is adjusted until 120 volts are applied. The jumpers for the voltmeter are then connected to the terminals for the PT transformer and the voltage is read and divided into 120. The result is compared against the nameplate on the regulator. A functional test of the regulator is next performed by moving the jumpers to connect the power source across the source and S/L bushings. The jumpers for the voltmeter are also connected across these bushings. The power source is adjusted until the voltage reads 120 volts. The jumpers for the voltmeter are next connected to the load and S/L bushings. The reading should still be 120 volts. The lamp and socket are also connected across the load and S/L bushings to test for continuity. The regulator is then raised and lowered through its operating limits while the test operator monitors the step change in voltage for each raise/lower step and also monitors the output of the lamp for continuity. The jumpers are disconnected and the equipment is removed at the end of the test.
During the tests, several jumpers have to be moved from one contact point to the next which often creates a confusing jumble of wires and the possibility of serious mistake. Further, when the bushings for the regulator being tested are located at the top of a utility pole or in some other inconvenient location out of reach, a separate trip up and down a ladder is required each time a jumper(s) must be connected or moved in the course of the test. This is unnecessarily time consuming. The use of a lamp and socket for testing continuity has also been found to be unreliable and to require too much operator attention.